After working with the telegram, Alexander Graham Bell started wondering about transmitting voice across the line. Intrigued, Bell started working on a device that would do that, the first telephone. For help, he hired Thomas Watson. Together worked on a prototype.
Of course, more than Bell had the idea of the telephone. In fact, Bell and a competitor Elisha Gray both worked on a prototype. Though I doubt literally, they raced to file a patent on the idea. Bell won. He received the patent on the device a few days before demonstrating the first prototype. It only worked for a few yards, but time would improve upon the invention until we now have the smartphone.